1. Field of the Invention
The present invention relates to a liquid discharge method and a liquid discharge apparatus for discharging a desired liquid by generation of bubble by thermal energy or the like and, more particularly, to a liquid discharge method and a liquid discharge apparatus using a movable separation film arranged to be displaced utilizing the generation of bubble.
It is noted here that xe2x80x9crecordingxe2x80x9d in the present invention means not only provision of an image having meaning, such as characters or graphics, on a recorded medium, but also provision of an image having no meaning, such as patterns, on the medium.
2. Related Background Art
One of the conventionally known recording methods is an ink jet recording method for imparting energy of heat or the like to ink so as to cause a state change accompanied by a quick volume change of ink (generation of bubble), thereby discharging the ink through an discharge port by acting force based on this state change, and depositing the ink on a recorded medium, thereby forming an image, which is so called as a bubble jet recording method. A recording apparatus using this bubble jet recording method is normally provided, as disclosed in the bulletin of Japanese Patent Publication No. 61-59911 or in the bulletin of Japanese Patent Publication No. 61-59914, with an discharge port for discharging the ink, an ink flow path in communication with this discharge port, and a heat-generating member (an electrothermal transducer) as energy generating means for discharging the ink located in the ink flow path.
The above recording method permits high-quality images to be recorded at high speed and with low noise and in addition, because a head for carrying out this recording method can have discharge ports for discharging the ink as disposed in high density, it has many advantages; for example, high-resolution recorded images or even color images can be obtained readily by compact apparatus. Therefore, this bubble jet recording method is used in many office devices including printers, copiers, facsimile machines, and so on in recent years and further is becoming to be used for industrial systems such as textile printing apparatus.
On the other hand, the conventional bubble jet recording method sometimes experienced occurrence of deposits due to scorching of ink on the surface of the heat-generating member, because heating was repeated in a contact state of the heat-generating member with the ink. In the case of the liquid to be discharged being a liquid easy to deteriorate due to heat or a liquid not easy to generate a sufficient bubble, good discharge is not achieved in some cases by formation of bubble by direct heating with the aforementioned heat-generating member.
Against it, the present applicant proposed a method for discharging an discharge liquid by generating a bubble in a bubble-generating liquid by thermal energy through a flexible film for separating the bubble-generating liquid from the discharge liquid, in the bulletin of Japanese Laid-open Patent Application No. 55-81172. The configuration of-the flexible film and the bubble-generating liquid in this method is such that the flexible film is formed in a part of nozzle, whereas the bulletin of Japanese Laid-open Patent Application No. 59-26270 discloses the configuration using a large film for separating the entire head into upper and lower spaces. This large film is provided for the purpose of being placed between two plates forming the liquid paths and thereby preventing the liquids in the two liquid paths from being mixed with each other.
On the other hand, countermeasures for giving a specific feature to the bubble-generating liquid itself and taking bubble-generating characteristics into consideration include the one disclosed in the bulletin of Japanese Laid-open Patent Application No. 5-229122 using a lower-boiling-point liquid than the boiling point of the discharge liquid, and the one disclosed in the bulletin of Japanese Laid-open Patent Application No. 4-329148 using a liquid having electric conductivity as the bubble-generating liquid.
However, the liquid discharge methods using the conventional separation film as described above are the structure of Just separating the bubble-generating liquid from the discharge liquid or simply an improvement of the bubble-generating liquid itself, and they are not at the level of practical use yet.
The present inventors have researched mainly liquid droplets discharged in discharge of liquid droplet using the separation film and came to the conclusion that the efficiency of liquid discharge based on formation of bubble by thermal energy was lowered because of intervention of change of the separation film, so that it had not been applied to practical use.
Therefore, the present inventors came to study the liquid discharge method and apparatus that achieved the higher level of liquid discharge while taking advantage of the effect by the separation function of the separation film.
The present invention has been accomplished during this study and provides breakthrough liquid discharge method and apparatus that are improved in the discharge efficiency for discharge of liquid droplet and that stabilize and enhance the volume of liquid droplet discharged or the discharge rate.
The present invention can improve the discharge efficiency in the liquid discharge method and apparatus using a liquid discharging head comprising a first liquid flow path for discharge liquid in communication with an discharge port, a second liquid flow path containing a bubble-generating liquid so as to be capable of supplying or moving the bubble-generating liquid and having a bubble-generating region, and a movable separation film for separating the first and second liquid flow paths from each other, and having a region of displacement of the movable separation film upstream of the discharge port with respect to a direction of flow of the discharge liquid in the first liquid flow path.
Particularly, the present inventors found out the following problem. When the space becoming the bubble-generating region is a small space, that is, when the bubble-generating region itself, though being formed on the upstream side of the discharge port with respect to the direction of flow of the discharge liquid, has the width and length close to those of the heat-generating portion, in generation of bubble in the bubble-generating region, the movable film is displaced with generation of bubble only in the perpendicular direction to the direction of discharge of the discharge liquid, so that sufficient discharge rates cannot be attained. This resulted in the problem that the efficient discharge operation was not achieved. Noting that the cause of this problem is that the same bubble-generating liquid is always used repetitively only in the small space closed, the present invention also realizes the efficient discharge operation.
A first object of this invention involves a liquid discharging method for discharging liquid from a discharge port by displacing, using a bubble generated at a bubble generation area for generating the bubble in the liquid, a movable separation film. That film substantially separates from each other a first liquid flow path communicating with the discharge port for discharging the liquid and a second liquid flow path having the bubble generation area. This method includes the steps of generating a bubble in the bubble generation area and displacing the movable separation film substantially without stretch in accordance with the generating step to discharge liquid from the discharge port.
A second object of this invention concerns a liquid discharging apparatus having a first liquid flow path communicating with a discharge port for discharging liquid, a second liquid flow path having a bubble generation area for generating a bubble in the liquid, and a movable separation film substantially separating the first from the second liquid flow paths. The movable separation film is displaced by the bubble generated at the bubble generation area to discharge the liquid from the discharge port, and the movable separation film is a thin film without substantial elasticity.
Another object of the present invention is to provide a liquid discharge method and a liquid discharge apparatus employing the structure for substantially separating or, more preferably, perfectly separating the discharge liquid from the bubble-generating liquid by the movable film, wherein in deforming the movable film by force generated by pressure of bubble generation to transmit the pressure to the discharge liquid, the pressure is prevented from leaking to upstream and the pressure is guided toward the discharge port, whereby high discharge force can be achieved without degrading the discharge efficiency.
Still another second object of the present invention is to provide a liquid discharge method and a liquid discharge apparatus that can decrease an amount of deposits depositing on the heat-generating member and that can discharge the liquid at high efficiency without thermally affecting the discharge liquid, by the above-stated structure.
Yet another object of the present invention is to provide a liquid discharge method and a liquid discharge apparatus having wide freedom of selection, irrespective of the viscosity of the discharge liquid and the formulation of material thereof.
For achieving the above objects, the present invention provides a liquid discharge method having a step of displacing a movable separation film for always substantially separating a first liquid flow path in communication with an discharge port for discharging a liquid from a second liquid flow path comprising a bubble-generating region for generating a bubble in said liquid, on the upstream side of said discharge port with respect to flow of the liquid in said first liquid flow path,
said liquid discharge method comprising a step of displacing a downstream portion of said movable separation film toward said discharge port relatively more than an upstream portion of said movable separation film with respect to a direction of the flow of said liquid.
Here, if the above step is carried out after midway of a growing process of bubble, a further increase will be achieved in the discharge amount. If the above step is carried out continuously substantially after the initial stage of the growing process of bubble, a further increase will be achieved in the discharge rate.
The displacement of the movable separation film can be controlled as desired or as stabilized by direction regulating means for regulating the displacement of the movable separation film in the above step.
Specific structures for carrying out the above displacing step, which is the feature of the present invention as described above, include those in the embodiments described hereinafter. In addition, the present invention involves all that can achieve the above displacing step by other structures included in the technological concept of the present invention.
Further, if the shape of the movable separation film is preliminarily determined or if the movable separation film is provided with a slack portion, the movable separation film itself will not need to extend with generation of bubble, which raises the discharge efficiency and which permits the movable separation film itself to regulate the displacement.
If the displacement of the movable separation film is regulated by regulating the growth of bubble in the second liquid flow path, direct action will take place on the bubble itself, whereby the displacement of the movable separation film is regulated from the initial stage of generation of bubble.
Here is a typical example of the structure of the device according to the present invention. The xe2x80x9cdirection regulating meansxe2x80x9d stated herein includes all arrangements of the movable separation film itself (for example, distribution of modulus of elasticity, a combination of a deformably extending portion with a non-deforming portion, etc.), all arrangements of the second liquid flow path itself (control of the heat-generating member or the bubble itself, etc.), an additional member acting on the movable separation film, structures of the first liquid flow path, and all combinations thereof. The typical structure according to the present invention is a liquid discharge apparatus having at least a first liquid flow path in communication with an discharge port for discharging a liquid, a second liquid flow path comprising a bubble-generating region for generating a bubble in said liquid, and a movable separation film for always substantially separating said first liquid flow path from said second liquid flow path,
said liquid discharge apparatus comprising direction regulating means for displacing said movable separation film on an upstream side of said discharge port with respect to flow of the liquid in said first liquid flow path and for displacing a downstream portion of said movable separation film toward said discharge port relatively more than an upstream portion of said movable separation film with respect to a direction of the flow of said liquid.
In the present invention of the above structure, the movable separation film provided above the bubble-generating region is displaced into the first liquid flow path with generation and growth of the bubble in the bubble-generating region. On that occasion, the downstream portion of the movable separation film is displaced into the first liquid flow path more than the upstream portion of the movable separation film, so that the pressure due to the generation of bubble is guided toward the discharge port of the first liquid flow path. By this, the liquid in the first liquid flow path is discharged efficiently through the discharge port with generation of bubble.
In the case wherein the deforming region of the movable separation film is provided with a slack portion, the slack portion is displaced in a curved shape with generation and growth of bubble and, therefore, the volume of the bubble acts more effectively on deformation of the movable separation film, thereby discharging the liquid more efficiently.
In the case wherein a movable member is provided adjacent to the movable separation film on the first liquid flow path side of the movable separation film and wherein the movable member has a free end on the downstream side of an upstream edge of a portion facing the bubble-generating region and a fulcrum on the upstream side of the free end, the displacement of the movable separation film to the second liquid flow path is suppressed upon collapse of bubble, which prevents movement of liquid to upstream, thereby improving refilling characteristics and decreasing crosstalk.
When the shape of the second liquid flow path is one capable of readily guiding the pressure due to the bubble generated in the bubble-generating region to the discharge port, the liquid in the first liquid flow path can be discharged through the discharge port efficiently by generation of bubble.
When the shape of the first liquid flow path is such that the height is smaller upstream than downstream, the downstream portion of the movable separation film is displaced more into the first liquid flow path than the upstream portion of the movable separation film, whereby the pressure due to the generation of bubble is guided to the discharge port of the first liquid flow path, so that the liquid in the first liquid flow path is discharged efficiently through the discharge port by the generation of bubble.
When the movable separation film is formed so that the thickness thereof on the downstream side is smaller than that on the upstream side, the movable separation film becomes easier to deform toward the discharge port with growth of bubble in the bubble-generating region, whereby the liquid in the first liquid flow path is discharged efficiently through the discharge port.
When the movable separation film is provided with a convex portion which projects into the second liquid flow path upon non-generation of bubble and which projects into the first liquid flow path upon generation of bubble, the pressure due to generation of bubble in the bubble-generating region is guided to the discharge port of the first liquid flow path by the convex portion, whereby the liquid in the first liquid flow path is discharged efficiently through the discharge port by the generation of bubble. Further, if the volume inside the convex portion is smaller than the maximum expansion volume of the bubble generated in the bubble-generating region, the amount of displacement of the convex portion will be kept constant even with dispersion in the expansion volume of bubble due to the discharge characteristics of liquid, thus realizing good discharge without dispersion between nozzles.